The present invention relates to the field of electronic imaging devices, and more particularly to a method and apparatus for precision optical adjustment of a field lens for an imaging device such as a liquid crystal display (xe2x80x9cLCDxe2x80x9d) imaging device. The predominant current usage of the inventive precision field lens adjustment apparatus is in the mounting and adjustment of reflective imaging devices in a multi channel projection system, wherein it is particularly important to maintain a precise relationship between a reflective surface of the LCD and a mounting surface.
Projection type imaging devices commonly use micro LCD imagers. Since the pixel size and spacing on these imagers are so small, they must be precisely placed in relation to the surface whereon they are mounted. Further, the imager must be kept perfectly aligned in tilt, since even the slightest distortion of the imager will result in a portion of the imager""s pixels being out of the focal plane and/or out of alignment. Moreover, it is important to maintain the tilt relationship of the field lens and the imaging device in order to maintain uniformity of the focal plane and to enhance convergence with other such devices in the system. It is known in the art to mount an LCD imager to a lens and further to provide some means for very minute adjustment of the lens for focusing purposes, and the like. Typically, the lens is provided with an apparatus such that the lens is screwed in or out in relation to the LCD imager by rotating the lens. This sort of apparatus will work reasonably well where a symmetrical lens is used, although minor imperfections in the lens and/or the mounting thereof my result in some undesirable effects when such lens is rotated.
It has been found to be necessary or desirable in some imaging systems to illuminate the LCD imagers off axis (i.e., not perpendicular to the plane of the imager""s surface). In such systems it is necessary or desirable to precompensate the image by using a decentered portion of the field lens. In such instances, it would take up unnecessary space and weight to include an entire lens, where only a section of the lens is to be used. Therefore, the field lens will most desirably consist of only a section of a complete lens. Due to the off-axis architecture and the use of a decentered, sectioned lens, the lens cannot be easily adjusted by rotating the lens.
It would be desirable to have a method or apparatus that facilitates fine adjustment of a decentered field lens in an off axis LCD imager apparatus. However, to the inventor""s knowledge, no such method or apparatus has existed in the prior art.
Accordingly, it is an object of the present invention to provide a method and apparatus for mounting an imaging device which does not put any stress on the imaging device which might tend to deflect it and cause some distortion from its flat, unstressed condition.
It is another object of the present invention to provide a method and apparatus for mounting an imaging device which will hold the imaging device securely such that it is resistant to vibration and other external forces.
It is still another object of the present invention to provide a method and apparatus for mounting an imaging device which is easy and inexpensive to implement in a production environment.
It is yet another object of the present invention to provide a method and apparatus for mounting an imaging device which will result in a clearly focused image across the entire surface of the imaging device.
It is still another object of the present invention to provide a method and apparatus for mounting an imaging device which will allow for fine adjustment of a field lens without rotating the field lens.
It is yet another object of the present invention to provide a method and apparatus for mounting a field lens to an LCD imager which will allow for the use of a partial lens.
It is still another object of the present invention to provide a method and apparatus for mounting a field lens to an LCD imager which will prevent dust from getting between the LCD imager and the field lens.
Briefly, an embodiment of the inventive adjustment apparatus has a field lens affixed within a field lens mount, the field lens mount has external threads to mate with an internally threaded ring. The internally threaded ring is held in place by a retainer and may be turned within an assembly housing to move the field lens mount relatively in and out in relation to an LCD imager. There are two holes going through the mount which slip over two fingers extending from the assembly housing to prevent the field lens mount and attached lens from rotating relative to the housing.
The invention permits a decentered field lens to be mounted in such a way that it can be axially adjusted relative to an imager and still maintain a dust free air gap between the field lens and the imager.
An advantage of the present invention is an image is produced which is in focus in all areas of the image.
Another advantage of the present invention is that a decentered field lens can be adjusted.
Still another advantage of the present invention is that a portion of a field lens can be used to save weight and space.
Yet another advantage of the present invention is that it is easy and inexpensive to implement.
Still another advantage of the present invention is that an imaging device is securely mounted.
Yet another advantage of the present invention is that it is simple and inexpensive to manufacture and to use.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawing. The objects and advantages listed are not an exhaustive list of all possible advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application.
Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above described objects and advantages. Accordingly, the listed advantages are not essential elements of the present invention, and should not be construed as limitations.